Adsorption Performance and Reuse Potential of a Green Alga for the removal of an Acidic dye from Synthetic Wastewater

Abstract

In the present study a Charophyta green alga Chara sp. has been proven to be a very effective and promising adsorbing biomass for the removal of an acidic dye, Methyl Orange [MO] from synthetic wastewater. Adsorption efficiency of alga was studied as a function of various operative variables, such as the contact time to reach equilibrium, pH of an aqueous solution, adsorbent dosage, and temperature for dye removal. The experimental data were analyzed by Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) models of adsorption isotherms, and best fit results were found for the Langmuir isotherm model, based on its correlation coefficient values. Pseudo-first-order and Pseudo-second-order kinetic models were applied to describe the adsorption process. It was found that the adsorption of methyl orange could be best described by the pseudo-second-order model. Values of Gibbs free energy (ΔG), entropy ((ΔS), and enthalpy change (ΔH) indicated the spontaneity, randomness, and endothermic nature of the reaction. FTIR studies showed the involvement of carboxyl, hydroxyl, and amide groups in the adsorption process. SEM micrographs displayed the morphological changes on the adsorbent surface, and BET analysis determined the surface area. To check the adsorbent reusability, repeated adsorption-desorption experiments were carried out for five consecutive cycles. The result shows that Chara sp. could be an effectual and reasonable adsorbent material for the management of MO-bearing wastewater.